Creating a 'locked' PDF?

That's definitely a valid concern... Is this what you're talking about (see image below)?

All I know about that is that particular option is that when I set the bottom two checkbox settings, I was still able to edit the text of the PDF in Adobe Acrobat. So you might have to look at a PDF processor more powerful than Preview or Pages. :/

Ben,

Neither Pages, nor the print panel PDF sub-menus expose the PDF controls that are required to modify user permission feature access to the PDF. You will need a PDF editor to enable the individual user access settings as a post-processing activity.

Consider using a trial of PDFpen 9 or PDFpenPro 9 editors to see how these settings are managed. Although these applications are in the Mac App Store, the vendor site offers the watermarked trial. You will have to set a password that controls the features that you want to limit, but does not impact the user's ability to open or read the PDF, or access features that you have allowed.

LibreOffice v5.4.5 and v6.0.2 can open a PDF via the File Open panel. You can then choose File menu : Export to PDF…, and on that panel, select the Security tab. This will allow you to set a PDF with a permissions (not open) password that limits feature access for the exported PDF.

With that clarification, the answer to your question is no. I haven't ever seen an option in Preview (or Pages) to prevent editing on a PDF. There is only one way that you could potentially prevent editing and it is (by no means) foolproof. Here's the explanation from the Preview Help Menu:

Lock PDFs and images

You can lock a PDF or image so that it can’t be edited or deleted. If you own a locked document, you can edit the document after unlocking it. Others can change the document’s contents only by creating a duplicate of the document and editing the duplicate.

Lock or unlock a PDF or image open in Preview: Move the pointer next to the document’s name in the title bar, click the arrow that appears, then select or deselect the Locked checkbox.

Tip: To lock or unlock a file in the Finder, select the file, choose File > Get Info, then select or deselect the Locked checkbox.

See also

Manage versions of a Preview document

Share your images or PDFs

Password-protect a PDF

Note that I removed links from the quote just because they won't lead to anything that's actually on a website. This locking feature doesn't prevent people from just creating duplicates and editing the duplicates, but it does seem to preserve the original.

The other thing you could try is BlueBeam's Revu. I don't know for sure if they allow you to edit security settings, but I really have no doubt that they do. BlueBeam is really overkill for your application, but they do have a 30-day free trial... https://www.bluebeam.com/solutions/revu-mac

When you are in Pages, go to 'Export To' (File>Export To) and select PDF. Then check the box marked 'Require a password to open.' 🙂